fix(audio): detect transcript-wide hallucinations

tests/test_api.py

@@ -638,6 +638,9 @@ def test_transcript_coverage_pagination_and_manual_reindex(tmp_path: Path, monke
             assert payload["items"][0]["start_ms"] == 10_000
             assert payload["detected_language"] == "zh"
             assert payload["quality_state"] == "ready"
+            assert payload["aggregate_risk"] is False
+            assert payload["repeated_phrases"] == []
+            assert payload["quality_score_semantics"] == "rule_check"
             assert payload["quality_flags"] == []
 
             speech = await client.get("/api/v1/speech/config", headers=headers)